There is many ways to measure strain state in materials. XRD rocking curve, SEM/EBSD, TEM/(ASTAR, TOPSPIN, TKD) is possible solution for your answer. In my case, I prefer the SEM/EBSD technique to measure up the strain state :)

XRD is possible solution when your desired data is lattice strain state in interface (i.e. epitaxial growth between two distinctive materials)

If the your available option is XRD, rocking curve might be solution.

There are different types of strain. Strain of first order or lattice strain is strain working over the total work piece. This type of strain often may be measured by the sin(Phi)-method.

Mosaic spread and defects within epitactical prowth may be charakterized by rocking curves or reciprocal lattice mapping.

Micro strain epsilon is propably what you ask for. Micro strain is caused by point defects and causes fluctuations of the lattice parameter within a single crystallite. This causes peak broadening bs

bs = 4*epsilon0*tan(theta).

Because the angle dependence differs from peak broadening by crystallite size both effects may be separated if sufficient line widths at low and high Bragg angles may be scanned. The evaluation may be done graphically / numerically by a Williamson-Hall-plot or by using a fundamental parameter approach as it is implemented in the program TOPAS.

Additionla types of defects and types of strains exist, but a more detailed description is the task of books or papers about microstructure.

You should make clear what do you want. Why do you need lattice strain and which technique is able to give you a reliable answer. And you should consider that you will get what you were investigating. Nearly all techniques mentioned above are surface techniques, i.e. they describe the change of an idealized concept called crystal in practice. Sometimes caused by a free surface which enables an uncontrollable relaxation up to a implemented strain you are possibly interested in. In TEM you even have two surfaces which makes everything even more questionable. EBSD? Well, you can try this, but the biggest problem is possibly your sample preparation which remains or even implements additional strain. And you never know, when the pattern matches the strain condition you are looking for. Certainly, you can possibly measure something... (we can always measure something ...) but will this really be the strain you are interested in? XRD: in principle the opposite problem. It is an integrating technique which is only able to give you an average. For several applications (strain compensation up to depth 100µm and more it is a nice technique) it works really good. But for strong gradients it needs other techniques like synchrotron, and who has this in his neighborhood?

In summary: the idea is reasonable, but you should think, whether all these techniques really give you the answer you need. Therefore, tell us, what you are planning to investigate...